Study on histophysiological effects of benzo[a]pyrene on the gonad and reproductive hormones in female orange spotted grouper, Epinephelus coioides, under laboratory conditions

This study aimed to investigate the effects of benzo[a]pyrene (BaP) on pituitary-gonad axis of orange spotted grouper (Epinephelus coioides). Fish were injected with 0, 2, 20 and 200 mg/kg of BaP per body weight and were kept under laboratory conditions for 14 days. Plasma samples were taken at days 1, 4, 7, and 14 and changes in 17-β-Estradiol (E2), 17-OH-progesteron, GTH Ӏ and GTH ӀӀ were evaluated. Alterations of gonad tissue structure also were studied in treated fish. Exposure of fish to BaP resulted in a significant decrease of 17-β-Estradiol, 17-OH-progesteron and significant increase in GTH Ӏ and GTH ӀӀ plasma levels (P<0.05). Also, changes were observed in the ovarian tissue of BaP exposed fish including tissue disorganization, increase in choromatin-nocleulos and prenucleulos follicles, increase in interstitial connective tissue and atretic follicles and decrease in developed follicles. Based on the results, decreases in the levels of steroid hormones several days after BaP exposure is due to antistrogenic effects of this compound that acts via decreasing in estrogenic receptors. On the other hand, the increase in GTHs, 7 days after exposure, is because of negative feedback of steroid hormones.